Apparatus of this type usually have a metal sensor disposed upstream of the parting mechanism in the direction of movement of the bale. In a preferred embodiment the sensor is moved by the carriage on the parting device. If the sensor is actuated by impingement on metal, the parting mechanism is triggered after a brief delay.
However, that simple construction has defects. Two bands may be disposed directly one beside the other on the bale and are evaluated by the sensor as merely one actuation. This wrong evaluation results in the impacting blade parting only the first of the two bands. Shears cannot part either of the bands, since they are prevented from penetrating the bale by a second band.
Another disadvantage is found when changing over between bands and wires in bale packaging. Since a normal sensor is actuated when the metal is first detected, the parting mechanism is triggered at the start. If the triggering delay is so adjusted that bands are impinged upon in the center, values are not right for baling wires. The wires are impinged upon only by the edge of the impacting blade, resulting in increased wear on the blade, or the wires are not touched at all.